[c-nsp] BackupInterface & IPv6 - when will they work together?

[Garry]

Just wondering - is there any time schedule (or an IOS release I missed) 
where using IPv6 addresses on a Backup Interface will actually work 
instead of complaining about overlapping IP addresses?
I just tried with 12.4(13d) and 12.4(17a), but both still wouldn't let 
me configure the IPs ... kinda beats the purpose of having a backup 
interface ...

Tnx , -garry